The objectives of CA 10729-10 are to develop and maintain in vivo and in vitro a spectrum of transplantable hepatomas originated from rat liver hepatocytes. The growth rate of more than 40 transplantable hepatomas is determined by the months between serial transfers; this variation ranges from 0.5 months to more than 12.0 months, or more than 20 fold. The degree of differentiation is ascertained by histological examination. The fastest-growing tumors are poorly differentiated, the intermediate growth rate tumors are mostly well differentiated and the slowest growing tumors are predominately well to highly differentiated. These hepatomas are made available to many collaborators throughout this country and abroad. Because of the difference in growth rate and degree of differentiation, our spectrum of experimental models affords investigators many choices in determining the essential from the non-essential biochemical and biological changes that occur in the neoplastic transformation. Detailed records are kept on every transfer generation. The growth rate of this spectrum of tumors remains quite stable over long periods. The tumors grow satisfactorily only in the inbred rat strain of origin. This project is designed (1) to maintain a large pool of transplantable tumors to support collaborative studies, (2) to develop new transplantable tumors more like the tissue of origin, and (3) to help support a center of excellence in experimental cancer research in the Howard University College of Medicine.